If they can’t do ‘it’ - how can they have offspring?
(Just wonderin’, here)
As an after note:
Check your pings, ML - I’ll FReepmail you if you don’t get it.
It is the OFFSPRING who are mules. Not the parents. The parents are usually a donkey and a horse...two different species.
I assume that a Zebra and a Horse would have similar offspring, because they are very different species.